Referring to FIG. 7, description is provided hereinafter of a shape of an ABS in a head slider of a floating type head used in a disk drive unit of the prior art. FIG. 7(a) is a plan view of the disk drive unit of the prior art as observed from the ABS side, and FIG. 7(b) is a sectional view of the same taken along a line A-A′ in FIG. 7(a).
In FIG. 7, ABS 42 of head slider 41 faces a surface of a recording medium formed on a disk (not show in these figures), and it has three surfaces of different heights (i.e., distances from the disk surface), that are first surfaces 45 having a same height as an area around signal converting element 43 such as a magnetic head mounted to head mounting pad 44, second surfaces 46 having a slightly lower height (i.e., larger distance from the disk surface) than first surfaces 45, and third surfaces 47 having an even lower height than second surfaces 46. The disk, which faces ABS 42 of head slider 41, rotates in a direction toward the side where signal converting element 43 is mounted (at the bottom of FIG. 7(a)) from the other side opposite the signal converting element 43 (at the top of FIG. 7(a)), and therefore the rotation of the disk produces an air flow in the direction of arrow 48. This means the side opposite the side where signal converting element 43 is mounted is in a position of an air inflow side, and the side where signal converting element 43 is mounted is at an air outflow side.
When the disk rotates, it produces a viscous flow of the air in the close proximity of the disk surface. Since this viscous flow acts on ABS 42 of head slider 41 to generate a lifting force, signal converting element 43 mounted to head slider 41 floats above the disk surface with a very small clearance.
Main part 49a constituting the air inflow side of ABS 42 of head slider 41 is constructed of a material having comparatively high hardness, and another part 49b including signal converting element 43 at the air outflow side is constructed of Al2O3 in a manner to embrace signal converting element 43.
Although not shown in FIG. 7, head slider 41 equipped with signal converting element 43 is mounted to one end of a suspension arm (also called a load beam), and ABS 42 of head slider 41 is thrust against the surface of the disk by the suspension arm, as is well known. The disk is connected to and driven by a drive motor, and the airflow generated by rotation of the disk lifts head slider 41 off the surface of the disk when it overcomes the thrusting force. On the other hand, a converting element swing means such as the so called voice coil motor (not shown) provided on one end of a head suspension mechanism (also not shown) bearing the suspension arm drives and controls a position of the suspension arm in a manner so that it records or reproduces data on a given track position of the disk with signal converting element 43.
Description is provided next of some examples of the floating type magnetic head used in a hard disk drive unit and having an air bearing surface (“ABS”) designed to alleviate an impact for preventing a magnetic disk from being damaged when the magnetic head clashed against or slides on the magnetic disk.
As one example of such floating type magnetic heads, there is proposed a slider that has a structure comprising edges (i.e., ridge-like portions), each formed with two surfaces consisting of an air bearing surface and another surface, and corners, each formed with three surfaces consisting of the air bearing surface and two other surfaces, wherein the edges and the corners have different radii for their respective curvatures. In other words, the structure of this magnetic head has the slider provided with the air bearing surface, of which the edges formed with two surfaces have a smaller radius of curvature than that of the corners formed with three surfaces. This structure is said to have an effect of alleviating an impact upon contact of the slider with the magnetic disk and improving reliability of the magnetic head because of the air bearing surface having the curvatures around the ridges and the corners that face the magnetic disk (refer to Japanese Patent Unexamined Publication, No. H11-110935, for example).
As another example of the floating type magnetic heads, there is also proposed a head slider of a structure which comprises at least one buffer pad having a chamfered and smoothly rounded surface formed around a corner of a substrate of the head slider or the vicinity thereof. This structure is said to have an effect of avoiding a sharp corner of the head slider from coming in contact to the disk and reducing abrasion of the disk and the head slider even if the head slider collides against the disk, so as to improve resistance to impacts and achieve high reliability of the hard disk drive unit (refer to Japanese Patent Unexamined Publication, No. 2001-35111, for example).
Referring to FIG. 8, description is provided of certain sliders any of which can control a difference in floating height between an inner periphery and an outer periphery of a disk by making good use of dependency of it upon a yaw angle, as other examples of the floating type magnetic head. FIG. 8(a) is a perspective view of such a head slider of the prior art as observed from the ABS side, and FIG. 8(b) is a perspective view of still another head slider of the prior art observed from the ABS side.
For such sliders that can control the difference in floating height between the inner periphery and the outer periphery of the disk by taking advantage of the dependency upon the yaw angle, there is proposed head slider 103 of the structure shown in FIG. 8(a), which comprises dynamic pressure generating sections 102a and 102b for generating a dynamic pressure on their surfaces facing a disk (not shown), and negative pressure generating sections 181a and 181b provided within the same surface at the trailing side relative to the center thereof with respect to a rotating direction of the disk for generating a negative pressure, in order to suppress a decrease in the floating height or a change in the contacting force attributable to a change in the yaw angle during a seeking operation, and to achieve a low floating level of the head or a stable contact with a small loading pressure between the head and the disk. Also proposed is head slider 103 of the structure shown in FIG. 8(b), which comprises at least two dynamic pressure generating sections 102a and 102b having shapes of longer dimensions in a direction generally orthogonal to a rotating direction of a disk (not shown) than dimensions along the rotating direction, and arranged on a surface facing the disk along the rotating direction with a deep channel between them, and first recesses 126a and 126b formed in dynamic pressure generating section 102b located at the trailing side of the rotating direction to provide first raised portions 107a and 107b along the direction generally orthogonal to the rotation direction and second and third raised portions 106a and 106b extending forward in the rotating direction from both side ends of these first raised portions 107a and 107b (refer to Japanese Patent Unexamined Publications, Nos. H10-283622 and H11-16141, for example).
However, any of the above head sliders of the prior art gives rise to a problem that the signal converting element mounted on the head slider comes into abnormally close to a surface of the disk due to instability of a floating posture of the head slider, because there is a difference in circling velocity of the disk relative to the head slider between the inner periphery and the outer periphery of the disk due to the difference in radius when a signal converting element mounted on the head slider makes a seeking operation across the inner periphery and the outer periphery, and variations of the circling velocity depending on a position of the head slider relative to a radial distance of the disk often cause the floating posture of the head slider unstable, and changes in angle of the head slider relative to the direction of airflow also cause the floating posture of the head slider unstable during the seeking operation of the signal converting element. These head sliders also have another shortcoming when they are installed into downsized disk drive units for portable use. That is, if the disk drive unit receives an external disturbance of some kind such as a physical impact and the like, it causes the floating posture of the head slider unstable, thereby making the signal converting element mounted to the head slider come into abnormally close to the disk surface, or the head slider collides against the disk surface, resulting in damages to any of the head slider, the signal converting element and the disk.
Moreover, in the head slider of the structure having the dynamic pressure generating sections for generating a dynamic pressure on the surface facing the disk and the negative pressure generating sections provided within the same surface at the trailing side relative to the center thereof with respect to the rotating direction of the disk for generating a negative pressure, there is also a problem which needs to be solved. That is, since this structure has a protruding pad serving as the dynamic pressure generating section in the central portion at the air outflow side of the ABS of the slider, it is unable to produce the maximum pressure on the element under a given floating position, and this structure is liable to collision of the head slider against the disk due to an external disturbance when the highest surface of the protruding pad comes to a point of the lowest floating height.
Furthermore, there are also other problems in the head slider of the structure comprising at least two of the dynamic pressure generating sections having shapes of longer dimensions in the direction generally orthogonal to the rotating direction of the disk than dimensions along the rotating direction, and arranged on the surface facing the disk along the rotating direction with the deep channel between them, and the first recesses formed in one of the dynamic pressure generating sections located at the trailing side of the rotating direction to provide the first raised portions along the direction generally orthogonal to the rotation direction and the second and third raised portions extending forward in the rotating direction from the both side ends of these first raised portions. In other words, this structure is thought to achieve stability of the floating height of the head slider by pressures produced at both side portions of it when the head slider is lifted to a given floating height. However, if these side portions are designed to produce the pressure at the given floating height, they give rise to the problems that (1) another pressure produced by an area of the element becomes relatively weak, and the element becomes liable to come in contact with the disk, that is, this structure has a poor followability of the element to undulation of the disk surface, and (2) the side portions of the slider are liable to came in contact to the disk when the floating height of the slider changes (i.e., by tilting or rolling).